After a year of marriage, Ivette Zurita Serrano and her husband, Herbert, were ready to have a baby. But that changed when Ivette lost her job in 2009.

"I was let go right when we started thinking about having a family," Serrano said. "And who was going to hire me if I was pregnant?"

The couple put off plans for parenthood indefinitely, a decision that might reflect the country's uncertain economic climate.

According to a report released today from the Center for Disease and Prevention's National Center for Health Statistics, there has been a 4 percent drop in births in the U.S. from 2007 to 2009 -- the largest two-year decline in 30 years.

"Certainly the economy and war have been two of the biggest influences on birth rate historically," said Paul Sutton, statistician and lead author of the report.

The number of births in the United States reached an all-time high of 4,316,233 in 2007. The subsequent decline, which shows no sign of leveling off, mirrors the country's ongoing economic crisis -- an observation consistent with other recessions.

"The two-year decline was notable, but not truly of historic proportions when compared with the large, extended fertility declines in the early 20th century and in the 1960s and early 1970s," the authors wrote.

After the Great Depression of the 1930s, the biggest drop in birth rate followed the post World War II baby boom -- the so-called baby bust of the'60s and '70s.

Births Down Nationwide

The CDC report released today breaks down birth data by maternal age, race and geographical location. And not surprisingly, the biggest drop occurred in states hit hardest by the recession, including Florida, Arizona and California -- where the Serranos live in a one-bedroom apartment in a suburb of Los Angeles.

"It's kind of scary to think, 'OK, well, if we were to have a huge commitment of a family and a house, one of us would have to be working," Serrano said. "And what if I were to get let go again?"

In an April 2010 report from the Pew Research Center, researchers compared birth rates with per capita income and found the two were closely linked across economic ups and downs. They also found a strong association between the change in birth rates between 2007 and 2008, and a state's housing foreclosure rates in 2007.

Is Economic Uncertainty Shaping Birth Rates?

Although she's now working full-time, Serrano said she still worries about the economy and her job security. But the 30-year-old is hesitant to wait much longer.

"You're put in a situation where you're not in your 20s anymore, and you can't keep waiting and waiting and waiting," she said. "You don't have all that time anymore to keep waiting."

While birth rates fell nationwide among all major races, they rose among women over 40.

"Assuming that women are making the decision not to have babies, perhaps the younger ones are postponing. But as women get older, they maybe start to think, 'It's now or never,'" Sutton said.

Although birth rates dropped regardless of birth order, the magnitude of change was biggest for third-order births and progressively smaller for second- and first-order ones.

The Serranos hope, ultimately, to have two or three kids. But they'll have to move out of their one-bedroom apartment first.